Shielded plot sprayer

ABSTRACT

A mobile shielded plot sprayer including a wind shield having a side wall that defines an enclosed area, and a movable atomizer within the enclosed area. A track assembly is located within the enclosed area and supported on the windshield. The atomizer is part of a spray assembly mounted on the track assembly and is movable thereon in at least one horizontal direction relative to the wind shield. A reservoir integral with the spray assembly and adapted to hold a liquid spray composition is operatively connected to the atomizer to supply the spray composition thereto.

[0001] This Application claims the benefit of U.S. provisionalapplication Serial No. 60/101,965 filed Sep. 25, 1998.

FIELD OF THE INVENTION

[0002] This invention generally relates to agricultural field sprayingequipment, and more particularly to a plot sprayer useful in fieldresearch relating to biological effectiveness of agricultural chemicalson crops and weeds.

BACKGROUND OF THE INVENTION

[0003] Agricultural chemicals, including pesticides, plant growthregulators, foliar fertilizers, desiccants and the like, are typicallyapplied to plants or soil by spraying using various types and designs ofmobile spraying equipment. The agricultural chemicals are normallydiluted, dissolved or dispersed in a suitable liquid carrier, mostcommonly water, to form a composition that is suitable for spraying andis referred to herein as a “spray composition”. The application rate ofa sprayed chemical can be metered by controlling four factors: the rateof travel of the spraying equipment over the ground, the rate at whichthe spray solution is dispensed, the width of the swath being sprayed,and the concentration of the chemical in the spray solution.

[0004] Rate of travel of the spraying equipment, expressed, for example,in meters per second (m/s), is dictated by forward speed duringspraying, whether motion is imparted by human power, as in the case ofhand-held or backpack-mounted spraying equipment, or by mechanicalpower, as in the case of tractor-mounted spray equipment orpurpose-built motorized spray rigs.

[0005] Rate of dispensing, or output, of the spray solution, expressed,for example, in liters per second (l/s), is dictated by several factors:the number of simultaneously operating spray nozzles, the configuration,in particular the size of the orifice of each nozzle, the propulsionforce applied (normally provided by hydraulic pressure), and therheological properties of the spray solution, especially its viscosity.The term “nozzle” in the present context is to be understood to apply toany atomization means having the function of a nozzle. Similarly, theterm “orifice” in the present context is to be understood to apply tothe feature or part of any atomization means having the same function asthe orifice of a nozzle.

[0006] Spray swath width, expressed, for example, in meters (m), isdictated by the number of nozzles arranged on a boom disposedperpendicularly to the direction of travel of the spray equipment, thedistance between nozzles, the angular width of the conical or fan-shapedspray pattern generated by the orifice of each nozzle, the degree ofoverlap of adjacent spray patterns, and the height of the nozzles abovethe ground or plant target.

[0007] Concentration of the chemical in the spray solution, expressedfor example in grams/liter (g/l), is controlled by the operator duringpreparation of the spray solution, most commonly by mixing a measuredamount of a concentrate formulation having a known concentration of thechemical in a measured volume of water.

[0008] Chemical application rate is the product of the above parametersand can be expressed as

R=OC/TW

[0009] where R is chemical application rate, O is spray solution output,C is concentration of chemical in the spray solution, T is speed offorward travel and W is swath width. When T is expressed in m/s, W in m,O in 1/s and C in g/l, R is given in grams per square meter (g/m²).

[0010] Modern spray equipment can generally be fairly preciselycalibrated with respect to the above parameters to deliver a desiredchemical application rate. Under ideal weather conditions, suchcalibration leads to an actual application rate which is more or lessconstant and reproducible and which varies little (typically +/−10% orless) from the desired rate.

[0011] However, weather conditions are seldom ideal. In particular,wind, even a light wind, disturbs the spray pattern sufficiently tocompromise accuracy and precision of a well calibrated sprayer. Whenwind speed and direction vary constantly, a condition known asturbulence, this problem is still more acute. Turbulent air movementfrequently occurs near ground level even when air movement a few metersabove ground is non-turbulent. This turbulence is often furtheraggravated by motion of the spray equipment.

[0012] An additional source of variation in application rate, even whena sprayer is perfectly calibrated, is vertical movement or oscillationof the spray boom or nozzle caused by travel over an irregular groundsurface by a wheeled vehicle carrying the spraying equipment. Suchvertical movement can be a problem also with hand-held spray equipmenteven when operated by an experienced technician walking on level ground.As the spray boom or nozzle is raised or lowered, spray swath width andthe degree of overlap of adjacent spray patterns vary, resulting inirregularities in deposition of the spray composition.

[0013] Yet another problem is disturbance of soil or plants immediatelybefore, during or immediately after spraying by the moving wheels of avehicle or the walking feet of an operator carrying the sprayingequipment. Such disturbance can take the form, for example, of localcompaction of the surface layers of soil, leading to variation in theeffectiveness of soil-applied chemicals. Disturbance of plants canaffect their biological response to an applied chemical as well asresult in accidental transfer of an applied chemical to other plants.

[0014] A particularly high degree of accuracy, precision andreproducibility is required when the chemical application is forresearch purposes. Agricultural researchers must be able to preciselyevaluate the effects of particular rates of a chemical on crop and/orweed plants occupying a particular area of a field demarcated for suchevaluation. Such a demarcated area is referred to herein as a plot.Typically, researchers compare the performance of plants in a sprayedplot to that in a nearby or adjacent unsprayed control plot. Generally,several different chemical treatments are compared, each treatment beingapplied to a different plot. It is important, therefore, that thechemical is precisely dispensed only on the intended plot, and uniformlywithin that plot, with little or no wind-assisted drift of the spraysolution on to adjacent plots.

[0015] The occurrence of wind is, in most climates, very frequent. Ifspraying has to be restricted to periods of relative calm, the number ofplots that can be sprayed in a season is limited. Research productivitysuffers as spray operators are often unable to apply chemicals at theoptimum time, because of windy weather. Thus, a need exists in the artfor a spraying apparatus which is able to accurately dispense a chemicalwithin a plot with minimum effects from wind and turbulence. Such anapparatus would greatly improve research productivity as well asaccuracy.

[0016] As spraying can seldom wait until conditions are absolutely calm,researchers have to some extent adapted their procedures to allow for atleast a light wind. For example, it is common to leave buffer stripsbetween plots to avoid wind-assisted drift from one plot contaminatingadjacent plots. The need for buffer strips increases the amount of landneeded for field testing of agricultural chemicals, or reduces thenumber of treatments that can be accommodated in a single experiment. Asthe experimental area becomes larger, variability in soil and plantconditions increases, tending to reduce the precision of the experiment.A further benefit of a windproof spraying apparatus would therefore beto reduce the amount of land required for a field experiment and therebyto improve the precision of such an experiment.

[0017] Previous attempts to provide spraying equipment with windprotection have involved partially or totally surrounding a spray boom,or individual spray nozzles on a boom, with a shield or skirt which iscarried on the boom. Shielded sprayers of this type do reducewind-assisted drift of spray solution, and can also be used to protectplants sensitive to a chemical from spray application of the chemicalclose to such plants (for example, in selective application of aherbicide to weeds between the rows of a crop). However, a new problemis introduced which is of particular relevance in research plots. Theshield or skirt tends to become coated with the chemical and transferschemical to plants as it passes over them. Further, the spray solutiondrips from the bottom edge of the shield or skirt. In these and otherways, shielded sprayers of prior art contribute to inaccuracy ofapplication.

[0018] There is a long-standing need for improved spraying apparatusthat can precisely apply an agricultural chemical treatment to a plot invariable wind conditions, and that minimizes the need for buffer stripsbetween plots. An improved spraying apparatus that meets this need, andat the same time eliminates vertical movement or oscillation of thespray boom or nozzle would be a particularly useful advance in the art.An improved spraying apparatus that has these benefits, and that inoperation causes no disturbance of soil or plants other than the directeffects of spraying, would be an even more useful advance in the art. Itis just such an improved spraying apparatus that is now provided.

SUMMARY OF THE INVENTION

[0019] The present invention relates to a spray apparatus for spraying aplot of land with a liquid spray composition. The spray apparatus isreadily relocatable without disassembly and comprises (1) a rigid frame;(2) a wind shield, supported on or integral with the frame, comprising aside wall that defines an enclosed area and has a top edge that ispreferably substantially horizontal and is located at a suitable height;(3) a track assembly located within the enclosed area and supported onthe frame; (4) a spray assembly mounted on the track assembly andmovable thereon in at least one horizontal direction relative to thewind shield, the spray assembly comprising atomizing means located at aheight lower than any substantial part of the top edge of the side wall;(5) a permanent or replaceable reservoir external to or integral withthe spray assembly, adapted to hold a liquid spray composition andoperatively connected to the atomizing means to supply the spraycomposition thereto; (6) means for transmission of power to the sprayassembly for movement thereof on the track assembly; (7) drive controlmeans, to permit operator control of said movement of the sprayassembly; (8) fluid propulsion means, i.e., means for causing the spraycomposition to flow from the reservoir through the atomizing means, toeffect spraying; (9) flow control means, to permit operator control ofspraying; and (10) means for moving the apparatus vertically andhorizontally, such that the apparatus is readily relocatable withoutdisassembly.

[0020] By “readily relocatable” it is meant that the entire apparatuscan be transported laterally from one plot to another in a field by asmall number of persons acting together, or with the aid of conventionalfarm machinery. The frame is of such construction, and the othercomponents of the apparatus are disposed with respect to the frame insuch a manner, as to permit easy relocation of the entire apparatuswithout disassembly. Means for moving the apparatus vertically andhorizontally can take a number of forms. For example, the frame can beprovided with optionally retractable wheels, to enable the apparatus tobe moved laterally from one plot to another. Preferably, however, theframe is provided with lifting means, to facilitate raising of theentire apparatus off the ground at the location of a first plot,transporting of the apparatus to the location of a second plot, andlowering of the apparatus on to the ground at the location of the secondplot. Such lifting means can be, for example, a plurality of handles topermit raising, transporting and lowering by two or more persons. Inpreferred embodiments, the lifting means are hitching means, by whichthe apparatus can be hitched to a tractor or other powered vehiclecapable of raising, transporting and lowering the apparatus. Suchhitching means typically comprise a plurality of hitching points and canbe adapted, for example, for connection to a conventionaltractor-mounted three-point hitch or fork-lift device.

[0021] The side wall of the wind shield preferably comprises foursubstantially rectangular side panels that are substantially verticaland are connected to each other at approximately 90° angles. The sidepanels can be of substantially equal length so as to define a squareenclosed area; however for most applications it is preferred that therebe a longer pair and a shorter pair of opposing side panels, therebydefining a substantially rectangular enclosed area. The wind shieldpreferably further comprises a substantially horizontal, square orrectangular top canopy which is connected to the side wall, for exampleat or close to the top edge thereof, so as to leave substantially nogaps between the top canopy and the side panels.

[0022] In one embodiment the side panels, and optionally the top canopy,are of rigid construction and have sufficient mechanical strength andrigidity to serve both as the wind shield and as the frame. In thisembodiment, therefore, the wind shield is integral with the frame.However, for most purposes it is preferred that the wind shield andframe are not integral, and that the side panels and top canopy areconstructed of a lightweight material attached directly to the frame. Itis especially preferred that this material be transparent, to permitoperation of the spray assembly within the enclosed area to be visuallymonitored by a person standing outside the wind shield.

[0023] It is also preferred that at least one of the side panels or thetop canopy be provided with an aperture large enough to permitinsertion, removal or servicing of a reservoir. This aperturefacilitates replacement or refilling of the reservoir after a plot hasbeen sprayed and the spray apparatus has been, or is about to be, movedto another plot.

[0024] The track assembly, in one embodiment of the invention, comprisesa single fixed horizontal track, typically oriented parallel to thelonger pair of side panels and midway between them. On such a track thespray assembly is movable in one direction only. In another embodimentof the invention, the track assembly comprises a first track mountedfixedly on the rigid frame and a second track mounted movably on thefirst track, both of these tracks being located within the enclosedarea. The first and second tracks are oriented perpendicularly to eachother, the first track being typically oriented parallel to the longerpair of side panels and midway between them. In this embodiment, thespray assembly is movably mounted on the second track. The first andsecond tracks are movably connected by a carriage. This arrangementallows the spray assembly to be moved across a plot in any desiredpattern, for example in a scan pattern that includes a series ofparallel passes.

[0025] The spray assembly comprises atomizing means which is preferablya hydraulic nozzle or a plurality of such nozzles. In an embodiment ofthe invention having a single fixed track on which the spray assembly ismounted, a preferred spray assembly comprises a boom orientedperpendicularly to the track, with a plurality of nozzles mounted atsubstantially regular intervals along the boom. The boom supports thenozzles and forms or carries a portion of a conduit through which aliquid spray composition can flow from the reservoir to all of thenozzles.

[0026] In a particularly preferred embodiment having only one nozzle,the spray assembly is movable horizontally in a first direction and asecond direction perpendicular to the first direction so as to becapable of uniformly spraying the entire enclosed area. This ispreferably accomplished using a track assembly comprising twoperpendicular tracks as described above, wherein the second track ismounted movably on the first track and the spray assembly is mountedmovably on the second track. Most preferably in this embodiment, thereservoir is integral with the spray assembly, i.e., is part of thespray assembly itself rather than being located elsewhere in theapparatus, and is connected to the nozzle by a rigid coupling piecehaving an internal conduit through which the spray composition is fedfrom the reservoir to the nozzle. This coupling piece can incorporate aquick-release coupling to permit easy replacement of the reservoir withminimal spillage of unused spray composition.

[0027] Drive means to cause the spray assembly to move on the trackassembly (including, in an embodiment with two perpendicular tracks,drive means to cause the carriage carrying the second track to move onthe first track) can be internal to the spray apparatus but ispreferably external, the spray apparatus itself having an operativeconnection to such external drive means. For example, the external drivemeans can comprise an electric power generator and the operativeconnection can comprise a power cable that leads to an electric motorforming part of the track assembly and providing motive force to propelthe spray assembly. As another example, the external drive means cancomprise a source of hydraulic power and the operative connection cancomprise a system of pipes providing hydraulic pressure to propel thespray assembly. In the embodiment described above wherein the trackassembly comprises perpendicular first and second tracks movablyconnected by a carriage, an operative connection to drive means isprovided both to the carriage, permitting movement of the second trackon the first track, and to the spray assembly, permitting its movementon the second track.

[0028] Drive control means can comprise electrical switches and/orhydraulic valves, operatively connected to a control panel. The drivecontrol means can be automated to varying degrees; in a preferredembodiment all aspects of motion and operation of the spray assembly,including spraying, are programmably controlled by a computer.

[0029] Fluid propulsion means, to cause the liquid spray composition toflow from the reservoir through the atomizing means, can be internal tothe spray apparatus or external thereto. Flow can occur by gravity feed,for example to a spinning disk atomizer which draws the spraycomposition through at a constant rate, controllable by the speed ofrotation of the spinning disk. Electrical power to drive a spinning diskcan be provided from an external source (e.g., a generator) or a sourcelocated within the apparatus (e.g. a battery pack). Preferably, however,the fluid propulsion means is hydraulic pressure provided by pressurizedgas, in which case the preferred atomizing means is a hydraulic nozzleor plurality of such nozzles. Pressurized gas, for example carbondioxide, nitrogen, air or propane, can be supplied from a bottle.Alternatively, it can be supplied directly from a compressor. In eithercase the pressurized gas is supplied to the reservoir by an airlinerunning from the source of pressurized gas to the reservoir. The term“airline” as used herein means a conduit for pressurized gas notrestricted to compressed air.

[0030] Flow control means typically comprises one or more valves in theairline and/or in a conduit through which the spray composition flowsfrom the reservoir to the atomizing means. Such valves can be designedfor manual operation or can be computer controlled. In the embodimentdescribed above wherein the track assembly comprises perpendicular firstand second tracks movably connected by a carriage, the flow controlmeans can be configured to cause spraying to occur when the sprayassembly is in motion in a first direction parallel to the first track,and to prevent spraying when the spray assembly is stationary or inmotion in a second direction parallel to the second track.

[0031] The present invention also relates to a process for spraying aplot using a spray apparatus as described herein. This process comprisesthe steps of (1) positioning the apparatus in a field such that theenclosed area defined by the wind shield covers the plot; (2) adding asuitable quantity of a spray composition to a permanent reservoir, orcoupling a replaceable reservoir containing a spray composition to aspray assembly adapted to receive such a replaceable reservoir; andthereafter (3) operating, or causing a computer control system tooperate, a switch or plurality of switches to cause the spray assemblyto move in a predetermined pattern across the plot and to spray thespray composition uniformly over the entire plot. Steps (1) and (2) ofthis process can be carried out in either order.

[0032] The spray apparatus of the invention is particularly adapted forconsecutively spraying a plurality of plots, for example inimplementation of an agricultural chemical field trial. Accordingly, aprocess is provided for consecutively spraying a plurality of plotsusing a spray apparatus as described herein, comprising carrying outsteps (1), (2) and (3) as described above; followed by (4) releasingunused spray composition from a permanent reservoir and rinsing thereservoir, or uncoupling a replaceable reservoir from the sprayassembly; and (5) repeating steps (1) to (4) with further spraycompositions on second and subsequent plots until all plots have beensprayed.

[0033] The present invention overcomes the problems of prior artsprayers by providing an easily relocatable, lightweight enclosure whichis stationary during operation and a spray assembly for spraying aliquid spray composition within the area defined by the enclosure, whichcan correspond to the area of a plot. The apparatus of the presentinvention provides more accurate application of spray compositions toplots, and more uniform application across a single plot than priorspray equipment. The improved accuracy and uniformity can result fromelimination of wind and turbulence, or from absence of vertical movementor oscillation of the spray assembly, or both. The apparatus alsoeliminates disturbance of soil or plants within plots by wheel-trackingor trampling. The present invention in one embodiment also permits rapidapplication of numerous spray compositions consecutively to differentplots, without the risk of contamination of one spray composition byremnants of a previously applied spray composition in the apparatus.Because of these and other advantages, agricultural researchers canapply spray compositions to test plots more rapidly and accurately thanin the past, and this can improve the speed, accuracy and productivityof their research.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034]FIG. 1 is a side elevational view of a spray apparatus accordingto the invention, mounted illustratively on a farm tractor.

[0035]FIG. 2 is a perspective view of a wind shield in accordance withthe invention.

[0036]FIG. 3 is a perspective view of a rigid frame, a wind shield and aspray assembly movably mounted on a track assembly located inside anenclosed area defined by side panels of the wind shield.

[0037]FIG. 4 is a perspective view of a track assembly and a sprayassembly in accordance with the invention.

[0038]FIG. 5 is an overhead view of an area enclosed by the wind shieldof a spray apparatus of the invention, the enclosed area comprising aplot to be sprayed.

[0039]FIG. 6 is a cutaway perspective view of an alternative embodimentof a spray apparatus having a wind shield that serves also as a rigidframe in accordance with the invention.

[0040]FIG. 7 is an end elevational view of a first track and carriage ofa spray apparatus in accordance with the invention.

[0041]FIG. 8 is a perspective view of a wind shield having mountedthereon an external rack of spray bottles (replaceable reservoirs) inaccordance with an embodiment of the invention.

[0042]FIG. 9 is a side elevational view of a spray assembly of oneembodiment of the invention.

[0043]FIG. 10 is a side elevational view of an improved spray assemblyin accordance with a preferred embodiment of the invention.

[0044]FIG. 11 is an exploded view of part of the spray assembly of FIG.10.

[0045]FIG. 12 is a schematic diagram of the operating system of a sprayapparatus of the invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0046] The present invention provides a field plot spraying apparatusthat is particularly suited for agricultural research purposes. Theapparatus includes a wind shield which during spraying is stationaryrelative to a plot of land, and provides an enclosed area around thatplot, and a spray assembly that moves within the enclosed area andrelative to the wind shield so that a liquid spray composition can beapplied to all or part of the plot. The wind shield is mounted on arigid frame and the whole apparatus is readily relocatable from one plotto another without disassembly.

[0047] One embodiment of the wind shield and frame is shown in FIG. 1.The wind shield 22 is attached to and substantially covers the frame 20which is capable of supporting the entire weight of the apparatus. Theframe can be hitched to a vehicle such as a farm tractor 12 by means,for example, of a standard three-point hitch (obscured in FIG. 1 by therear tire 14 of the tractor). The three-point hitch can be used to liftthe apparatus off the ground and hold it in an elevated position whilethe tractor drives to a different location, carrying the apparatus alongwith it. When the tractor arrives at the new location, the apparatus canbe lowered., again by means of the three-point hitch, so that bottomhorizontal members 34 a-34 d of the frame 20 rest on the ground.Although the apparatus of the present invention could be used forspraying while the bottom horizontal members 34 a-34 d are lifted offthe ground, it is preferred to spray with the lower edge of the windshield 22, which in this embodiment is contiguous with the bottomhorizontal members 34 a-34 d of the frame 20, touching the ground inorder to minimize wind-induced distortion of spray patterns.

[0048] The apparatus could be moved by other means, such as a fork lift,or manual lifting by several people. However, it will usually be mostefficient to lift, lower, and move the wind shield with a farm tractoras in FIG. 1 or a functionally equivalent vehicle such as a truck. Thetractor can also provide electrical or hydraulic power for moving thespray assembly (described below) within the enclosure defined by thewind shield, and/or for compressing gas to pressurize the reservoircontaining the liquid composition to be sprayed.

[0049] The wind shield 22, shown without the tractor in FIG. 2, ispreferably constructed of a flexible material securely attached to theframe 20. The wind shield 22 of FIG. 2 has a side wall comprising fourside panels 24 a-24 d and a top canopy 26. The side panels 24 a-24 d andthe top canopy 26 are preferably rectangular and joined to each other at90° angles. The side panels 24 a-24 d and top canopy 26 define anenclosed area. The horizontal dimensions of the area enclosed by thewind shield 22 are preferably either equal to the size of the plot to besprayed or somewhat larger than the plot in order to allow a buffer zoneat the edges of the enclosed area.

[0050] Horizontal dimensions of the enclosed area, and hence of a plotfor which the apparatus is a useful spraying device, are not narrowlylimited. For example, an enclosed area having length and breadth each ofabout 1 to about 10 m can readily be provided. Illustratively, a lengthof about 5 m and breadth of about 2.5 m have been found to beconvenient. Height of the top canopy, or of the top edge of the sidepanels in the absence of a top canopy, is likewise not narrowly limited.the primary requirement being that the spray apparatus can beaccommodated such that the atomizing means is at a suitable height forspraying while at the same time no higher than the top edge of the sidepanels. Where a top canopy is present, the entire spray assembly istypically below the top canopy. These considerations normally dictate aminimum height above ground (when the apparatus is in position forspraying) of the top canopy or of the top edge of the side panels ofabout 0.5 m, but for most applications a minimum height of about 1 m ismore appropriate. Apparatus of the invention can be purpose-designed fora wide variety of situations. including for use in tall-growing crops orother vegetation, thus the top canopy or the top edge of the side panelscan be up to about 3 m, or even more, above ground. For use on bare soilor low-growing crops or weeds, it is more convenient for the height ofthe top canopy or the top edge of the side panels to be no more thanabout 2 m.

[0051] The frame 20 is rigid and preferably made of a lightweightmaterial such as aluminum or fiberglass. The frame can comprise aplurality of individual structural members that are rigidly connected,for example by bolts or welds. Suitable materials for the wind shield 22include canvas, woven polypropylene and polyethylene film. It ispreferred for this material to be transparent in order to allowobservers to visually monitor the spray operation within the enclosedarea defined by the wind shield.

[0052] It will be appreciated that since the spraying apparatus isdesigned to be frequently moved to different plot areas, it needs to beanchored to the ground only sufficiently to prevent toppling ordislodgement by wind or other lateral forces. It will also beappreciated that many different anchoring methods can be employed,including relying on the weight of the apparatus itself in low windconditions. In high wind conditions, supplemental weights could be hungon the frame 20, or anchoring pegs could be driven into the ground andthe frame 20 secured to such pegs.

[0053] In another embodiment of the invention, a wind shield 10 isprovided in the form of a rigid four-sided box, as shown in FIG. 6, inwhich case the wind shield can function also as the frame on which otherparts of the apparatus are supported and to which a tractor or othervehicle can be hitched. In this embodiment, the wind shield 10 cansuitably include rigid side panels 74 and a rigid top canopy 72.

[0054]FIG. 3 shows a wind shield 22 constructed of transparent material,together with frame 20 and some of the internal components of thespraying apparatus. The specific embodiment shown in this figureincludes hooks 28 as alternative means for grasping and lifting the windshield. However, as explained above, it is usually preferable to connectthe frame 20 to a standard hitch such as a three-point hitch on a farmtractor (linkage not shown in FIG. 3). The frame 20 in this embodimentincludes corner vertical members 30 a-30 d, top horizontal members 32a-32 d, bottom horizontal members 34 a-34 d, and top struts 36 toprovide additional rigidity to the structure.

[0055] Where the track assembly comprises a single track, this track ispreferably medianly situated in the enclosed area and oriented parallelto the longer rather than the shorter sides of the wind shield. It canconveniently be attached, for example by bolts or welds, to the tophorizontal members 32 a and 32 c and to the top struts 36 of the frame20. The single track can comprise two parallel rails that can be engagedby wheels of the spray assembly, and a rigid support gantry whichensures the rails do not move relative to one another, potentiallycausing derailment or jamming of the spray assembly.

[0056] In the specific embodiment illustrated in FIG. 3, the trackassembly comprises a first, or X-axis, track 42 medianly and fixedlymounted on the frame 20 and a second, or Y-axis, track 40 movablymounted on the X-axis track 42 and oriented perpendicularly thereto.This Y-axis track comprises a bar 50 having mounted movably thereon aspray assembly 45. The spray assembly includes a mounting bracket 46, anozzle 47 and a reservoir 48.

[0057] Turning to FIG. 4, which shows the Y-axis track 40 and the X-axistrack 42 without showing the frame 20, the mounting bracket 46 is inthis embodiment movably mounted on the underside of the bar 50 of theY-axis track 40, so that the spray assembly 45, which includes themounting bracket 46, nozzle 47 and reservoir 48, can be moved back andforth in the second direction, or Y-axis, within the area enclosed bythe wind shield. Preferably this is accomplished by including a pair ofrails on the underside of bar 50, with wheels (not shown) rotatablymounted at the top of the mounting bracket 46 movable on those rails.Pressure applied within the reservoir 48 causes a liquid spraycomposition therein to be emitted from the nozzle 47 in a spray pattern52 downwardly on to soil or plants.

[0058] The X-axis track 42 of the embodiment illustrated in FIG. 4includes a support gantry 54 which is fixedly attached to the frame 20(not shown), for example by welds or bolts. Thus, in operation, theX-axis track remains stationary relative to the frame and wind shield.The support gantry 54 can optionally have support struts (not shown) toprovide further rigidity. The X-axis track 42 also includes a pair ofrails 56 which are fixedly mounted on the support gantry 54, at least ateach end and preferably also at a plurality of points along theirlength. The rails 56 provide a path for wheels 58 which are rotatablymounted on a carriage 60 that is in turn fixedly attached to the Y-axistrack 40, thereby permitting the Y-axis track 40 to move back and forthin the first direction, or X-axis. In this manner the spray assembly 45can be moved in both the X- and Y-axes within the enclosure defined bythe wind shield.

[0059] An example of a suitable path for the movement of a single-nozzlespray assembly, in an embodiment of the invention having X-axis andY-axis tracks, is shown in the overhead view of FIG. 5. A plot 62 to besprayed is shown by the diagonal shading. The area 64 enclosed by thewind shield 22 is in this illustrative case larger than the plot, andincludes additional end regions 65 and 66, one on each end of the plot62. Within the area enclosed by the wind shield 22. the spray assemblyis moved in a scan pattern that includes a series of parallel passes.For example, the spray assembly begins at the location marked bycoordinates X_(0,) Y₀. When operation on a plot commences, the sprayassembly is first moved by drive means on the Y-axis track to coedinatesX₀, Y₁. Next, the Y-axis track carrying the spray assembly is move bydrive means on the X-axis track, so that the spray assembly proceedsfirst to coordinates X₁, Y₁ at the opposite end of the plot 62. Thespray assembly then moves on the Y-axis track to coordinates X₂, Y₂before proceeding to coordinates X₁, Y₂ by movement of the Y-axis trackon the X-axis track as before, but in the reverse direction. Bycontinuing this scan pattern across the plot as indicated by arrows 67a-67 d, and by activating the spray assembly during the time it ispassing over the plot in the X-axis, the entire plot 62 is sprayed.After the scan pattern is completed, the spray assembly returns to thestart coordinates (X₀, Y₀). Table 1 gives a suitable example of thesequence of moves for the spray assembly. TABLE 1 Move X location Ylocation start X₀ Y₀  1 X₀ Y₁  2 X₁ Y₁  3 X₂ Y₁  4 X₂ Y₂  5 X₁ Y₂  6 X₁Y₃  7 X₂ Y₃  8 X₂ Y₄  9 X₁ Y₄ 10 X₁ Y₀ 11 X₀ Y₀

[0060] Note that the spray assembly continues in the X-axis directionpast the ends of the plot 62. In one method of operation, sprayingcontinues throughout the entire travel time in the X-axis, thereby alsospraying portions of end regions 65 and 66 to form buffer zones 68. Inanother method of operation, spraying is automatically started andstopped during travel in the X-axis so that only the plot 62 itself isspray. With either method of operation, as a result of this extendedtravel beyond the limits of the plot 62, the buffer zones 68 provide foracceleration and deceleration of the spray assembly. Thus, during thetime the spray assembly is traveling in the X-axis over the plot 62 itis moving at substantially constant velocity across the plot, therebyenhancing uniformity of the rate of application of the spraycomposition.

[0061] As an example of suitable dimensions, the plot 62 can be 144inches (3.66 m) long in the X-axis and 96 inches (2.44 m) wide in theY-axis, the area 64 enclosed by the wind shield 22 can be 216 inches(5.49 m) long and 96 inches (2.44 m) wide, each buffer zone 68 can be 18inches (0.46 m) long and 96 inches (2.44 m) wide, the length 70 of sprayassembly travel in the X-axis can be 180 inches (4.57 m), the distance71 between the long side panel 69 of the wind shield 22 and the line ofthe first pass 67 a in the X-axis of the spray assembly can be 12 inches(0.30 m), and the distance between consecutive passes, for example 67 aand 67 b, in the X-axis can be 24 inches (0.61 m). This is consistentwith the entire width of the plot being sprayed with non-overlappingspray patterns in consecutive passes, and with a spray pattern width of24 inches (0.61 m).

[0062] In a preferred embodiment, the spray apparatus is arranged tospray only while the spray assembly is moving in the X-axis. In otherwords, in the particular embodiment illustrated in FIG. 5, while thespray assembly moves along segments 67 a-67 a d of the scan pattern, anopen valve (not shown) permits spraying to occur. At or before themoment when the spray assembly reaches the end of such a segment andstarts to move in the Y-axis, the valve closes to stop spraying. Thevalve limiting spraying to the time when the spray assembly is travelingin the X-axis can be triggered by any suitable switching device locatedon the X-axis track, or can be set to open automatically when travelbegins on a segment 67 a-67 d of the scan pattern and closeautomatically when travel is completed on such a seginent. The valveitself can be in an airline providing pressure to the reservoir, or inthe conduit for the spray composition leading from the reservoir to thenozzle of the spray assembly.

[0063] Drive means for moving the spray assembly 45 on the Y-axis track40 and drive means for moving the Y-axis track on the X-axis track 42can each take a number of forms. For example, an electric motor can beused to cause a chain or pulley to draw the carriage 60, which carriesthe Y-axis track 40, along the X-axis track 42, as shown in FIG. 7. Thepreferred drive means is a hydraulic or oil pressure operated system ofa kind well known in the agricultural machinery art, which providesseveral desired characteristics. For instance, such a system provides aconsistent controllable velocity. The system also provides forconsistent, repeatable and accurate stops of the spray assembly. Inaddition, the system provides for high rates of acceleration anddeceleration to maximize the portion of the total travel path of thespray assembly within which velocity is substantially constant.

[0064] Whether operated hydraulically or electrically, it is preferredthat operation of the sprayer be robotic or controlled electronically,for example by means of a programmable computer. Control systems for thetypes of motion described herein are commercially available, as arecontrol panels suitable for the present apparatus.

[0065] For an apparatus of the invention having a single track, drivemeans for movement of the spray assembly on the track can be asdescribed above for movement of the carriage on the X-axis track.

[0066]FIG. 12 shows, in schematic form, an operating system suitable fora spray apparatus of the invention. External drive means 121, which canbe, for example, an electric generator or storage battery, or ahydraulic power generating system, provides power for movement ofcarriage 124 on the track assembly (not shown). Power is supplied fromdrive means 121 to carriage 124 by transmission means 122, which in thecase of hydraulic power typically comprises a hydraulic pipe systemcontaining oil, and in the case of electric power typically compriseselectric cable connected to an electric motor situated in or on carriage124. Transmission means 122 is provided with drive control means 123,which can comprise one or more valves or switches and is, in a preferredembodiment, operated by electronic signals transmitted along cable 133from computer 132.

[0067] Also shown in FIG. 12 is the fluid propulsion means, typicallycomprising an external pressurizing means 125, such as a compressor orpre-pressurized gas cylinder, which feeds pressurized gas throughairline 126 to reservoir 128 of the spray assembly. The pressurized gaspropels a spray composition from reservoir 128 through conduit 129 toatomizing means 130, from which the spray composition emerges as a spray131. A flow control means is provided in the form of controllable valve127 located at a convenient point in airline 126; alternatively orsupplementarily a flow control means is provided in the form of acontrollable valve or shut-off in conduit 129 (not shown). The flowcontrol means is, in a preferred embodiment, operated by electronicsignals transmitted along cable 134 from computer 132.

[0068] In an agricultural research setting it is often useful to applynumerous spray compositions, each to a separate plot, so that theeffects of the compositions on plants, or on plant diseases, pests orpathogens, can be compared. In order to facilitate the application ofmany spray compositions one after another to successive plots withminimum loss of time between applications and with minimum opportunityfor error, the apparatus of the present invention can include a spraybottle rack. As shown in FIG. 8, in one embodiment the frame 20 hasmounted on it an external rack 80 which can hold numerous spray bottles82, each containing a liquid spray composition in an amount designed forapplication to a single entire plot. The rack is preferably positionedat the end of the apparatus proximal to the tractor, close to theoperating controls for maximum convenience and efficiency of operation.Preferably the spray bottles form replaceable reservoirs 48 (of FIG. 6),but in an alternative embodiment the contents of each spray bottle arepoured or drawn into a permanent reservoir.

[0069] A side panel 24 of the wind shield 10 preferably contains anaperture 84 to allow an operator to manually remove a spray bottle fromthe spray assembly inside the wind shield 10, select a new spray bottle82 from the rack 80, insert the new bottle through the aperture 84, andconnect the new bottle to the spray assembly. Most preferably, theaperture 84 is closeable, for example by means of a flap. Thus, adifferent spray composition can be applied to each plot on which theapparatus is successively placed, and a large number of plots can besprayed in quick succession with a high degree of precision.

[0070]FIG. 9 shows a portion of a spray assembly 88 of one embodiment ofthe invention in which pressurized gas, for example carbon dioxide atabout 28 psig (193 kPa), is supplied from an airline 89 through a bottomfitting 92 attached to a coupling piece 91 into which the neck of thespray bottle 90 can be inserted and held in position, for example by aconventional screw fitting. The pressurized gas passes from the bottomfitting 92 through the coupling piece up into the upper part of thespray bottle or reservoir 90 via a tube 94, and forces the liquid spraycomposition out through a conduit in the coupling piece into ahorizontal spray boom 96 attached to the coupling piece. From the sprayboom 96 the liquid spray composition is released through one or moredownward pointing nozzles 98. A valve 100 can be used to permit or stopflow of the spray composition into the boom 96.

[0071] One disadvantage of the spray assembly of FIG. 9 is that afterthe reservoir 90 is emptied, some of the spray composition will remainin the boom 96. If not completely ejected from the spray nozzles andboom, this remaining spray composition will contaminate the next spraycomposition used, and therefore may render the results of an experimentinaccurate (for example by causing a plot to receive a mixture of afirst herbicide composition and a second herbicide composition when theresearcher intended that plot to be treated only with the secondherbicide composition).

[0072]FIG. 10 shows a portion of an improved spray assembly 88 for usein a preferred embodiment of the present invention. A femalequick-connect fitting 102 extending to one side of a coupling piece 106is adapted to receive pressurized gas from an airline such as a hoseconnected to a gas bottle, air compressor or other source (not shown).The pressurized gas passes into a tube 104 which carries the gas throughthe coupling piece 106 to the upper part of the spray bottle orreservoir 101. The gas pressure within the reservoir 101 forces theliquid spray composition contained therein down through the couplingpiece 106 and a nozzle 108 attached directly to the bottom of thecoupling piece. The nozzle atomizes the liquid spray composition andcreates a downwardly-directed spray pattern 52. Each spray bottle on therack 80 shown in FIG. 8 preferably comprises all of the assembly shownin FIG. 10. Therefore, when a first spray composition has been appliedto a first plot from a first spray bottle, the spray apparatus can thenbe lifted and moved to a second plot, the first spray bottle can bemanually removed by releasing the quick-connect fitting 102 from theairline, a second spray bottle containing a second spray composition canbe selected from the rack 80, and it can then be attached to theairline, again by means of quick-connect fitting 102, so that the secondspray composition can then be applied to the second plot.

[0073] The preferred embodiment of spray bottle 82 is shown in anexploded view in FIG. 11. In this view, the various components of nozzle108 are shown as cap 110, seal gasket 112, spray tip 114, ball valvestrainer 116, and nozzle body 118. The various components of nozzle 108are commercially available, for example from Spraying Systems Co. ofWheaton, Ill.

[0074] Although in preferred embodiments the spray composition reservoirtakes the form of a replaceable spray bottle such as that illustrated inFIG. 10 and is mounted integrally on the spray assembly as describedabove, the spray composition could alternatively be stored in apermanent reservoir not part of the spray assembly itself. For instance,the reservoir could be mounted in a fixed position, for example on theframe 20, and be connected to the spray assembly by a flexible conduitso that a connection is maintained during the entire travel of the sprayassembly within the enclosure defined by wind shield 10.

[0075] Use of the shielded plot sprayer of the present invention hasproved to be a significantly improved method of spraying research fieldplots by comparison with conventional prior art methods. One majoradvantage is improved precision of evaluation of biologicaleffectiveness of test compositions on a variety of plant species. Thisimproved precision takes the form of reduced variability in data derivedfrom different test plots receiving the same treatment.

[0076] To illustrate this advantage of the invention, a field test wasimplemented on a farm in Illinois. Several annual broadleaf and grassspecies were planted in rows and were permitted to grow to a suitableplant growth stage for treatment with the post-emergence foliar appliedherbicide glyphosate. Sufficiently uniform populations of six of thesespecies established for evaluation of the herbicidal effectiveness ofglyphosate. The six species were velvetleaf (Abutilon theophrasti,ABUTH), morningglory (Ipomoea sp., IPOSS), prickly sida (Sida spinosa,SIDSP), common waterhemp (Amaranthus radis, ANIATA), spring wheat(Triticuin aestivum, TRZAS) and barnyardgrass (Echinochloa crus-galli,ECHCG). Plots were marked off in such a way that each plot extended overrows of all six species.

[0077] Eight herbicidal treatments were applied, one to a plot, in areplicated block experimental design with three replications of eachtreatment. A set of plots was left untreated as a control. The eighttreatments consisted of applications of two commercial isopropylammoniumglyphosate formulations, ACCORD® herbicide and ROUNDUP® ULTRA herbicide,both of Monsanto Company, each at four rates (0.14, 0.28, 0.56 and 1.12kilograms glyphosate acid equivalent per hectare). ROUNDUP® ULTRAcontains a surfactant and is designed to be used alone; ACCORD®herbicide contains no surfactant and is generally used with addition ofa surfactant adjuvant in the spray tank. In the present study, however,no surfactant was added. All applications were made in a water volume of93 liters per hectare.

[0078] The entire study was done four times in separate runs, with allruns being made concurrently one afternoon in August. At the time ofspraying, air temperature was 23° C., relative humidity 75% and a lightwind was blowing from a north-northwesterly direction at 11 km/h. Thiswindspeed is not normally considered excessive for conducting fieldspray trials. In one run of the study, a spray apparatus of theinvention, as illustrated in FIGS. 1, 3, 4, 6, 7, 8, 10 and 11 anddescribed in passages of text herein referring to these FIGS. was usedfor all treatments. In the other three runs, the treatments were appliedby hand-held boom sprayers operated by three different field researchtechnicians, all very experienced in conducting field tests such as thepresent study, and referred to herein as applicators 1, 2 and 3.

[0079] Twenty-six days after treatment (DAT), percent inhibition of allsix species in all plots was evaluated independently by two experiencedfield research technicians. Percent inhibition is a visual measurementof herbicidal effectiveness by comparison with untreated plots, whereina percent inhibition of 0% indicates no effect and a percent inhibitionof 100% indicates that all plants of a particular species in a plot werecompletely dead. A percent inhibition of 85% or more is in most casesconsidered acceptable for commercial herbicide use.

[0080] Thus the data set gathered from this study includes a total of288 data points (8 treatments×3 replicates×2 evaluators×6 species) foreach of the four runs, one of which is illustrative of the presentinvention and the other three are illustrative of a standard method inthe art. The data from each of the four runs were subjected to aseparate analysis of variance. It is generally recognized in the artthat analysis of variance of field data of the type generated in thisstudy is of doubtful value as a means of establishing significance ofdifferences among treatments, unless the data are subjected to anappropriate statistical transformation. This is because towards the topof the percent inhibition range, i.e., near 100%, within-treatmentvariances are normally much smaller than those in the middle or near thebottom of the range. For example, a highly effective herbicide treatmentapplied to a species in three replicate plots might give percentinhibition data of 92%, 95% and 97% respectively, while in the samefield test a less effective treatment might give percent inhibition dataof 40%, 60% and 72% respectively. “Least significant differences”established by analysis of variance of such data could lead tomisleading conclusions, underestimating the significance of smalldifferences in the commercial (≧85% inhibition) part of the range andoverestimating the significance of larger differences in the middle orlower part of the range.

[0081] For the present purpose, however, analysis of variance wasconducted not to attempt to discern differences among treatments but toestablish the error variance in each of the four runs of the test. Asthe spread of data was similar in all four runs, no seriousmisinterpretation results from analysis of the untransformed data;therefore no transformation was done. “Error variance”0 as used hereinis the mean square for error, derived from the error sum of squaresdivided by the number of degrees of freedom for error, in the presentcase 30. A large value of error variance indicates a high degree ofvariability from plot to plot within treatments; progressively lesserdegrees of variability are indicated by values of error variance tendingtowards zero.

[0082] Table 2 shows the mean percent inhibition for all eighttreatments in each run of the test, together with the error varianceapplying to that run. TABLE 2 percent inhibition, 26 DAT ABUTH IPOSSSIDSP AMATA TRZAS ECHCG average shielded sprayer of mean 60.92 47.8564.67 79.35 95.31 86.94 the invention error variance 54.33 192.17 106.25113.40 20.75 36.87 87.30 hand-held sprayer mean 66.19 48.63 64.60 69.6996.52 88.29 (applicator 1) error variance 104.24 209.09 109.43 109.1414.80 44.95 98.61 hand-held sprayer mean 60.25 45.35 57.17 63.29 95.9686.27 (applicator 2) error variance 53.18 238.16 155.44 140.46 25.5557.75 111.76 hand-held sprayer mean 74.79 54.50 69.81 78.79 95.42 89.40(applicator 3) error variance 88.70 275.16 177.65 114.61 47.08 77.68130.15

[0083] It will be noted that use of the shielded sprayer of theinvention provided the lowest error variance of the four runs of thetest for three of the six species (IPOSS, SIDSP and ECHCG). For ABUTH,the shielded sprayer of the invention provided close to the lowest errorvariance; only applicator 2 gave marginally lower but applicators 1 and3 gave much higher error variance. For AMATA, the shielded sprayer ofthe invention gave the second lowest error variance in the study,applicator 1 giving the lowest and applicator 3 coming close to matchingthe error variance of the shielded sprayer. For TRZAS, the shieldedsprayer again came second to applicator 1, but both applicators 2 and 3gave higher error variance. The average error variance across all sixspecies shows the shielded sprayer of the invention clearly to givelower overall error variance than any of applicators 1, 2 or 3 usingstandard hand-held spraying equipment.

[0084] The above study illustrates a surprising advantage of use of thepresent apparatus over a conventional method of field plot spraying,under light wind conditions normally considered acceptable for suchconventional method. The benefit of using the present apparatus will beconsiderably greater under more windy or turbulent conditions.

[0085] As a further illustration of the usefulness of the presentapparatus, a shielded sprayer similar to that used in the studydescribed immediately above has been used to conduct a field experimentinvolving spray application of a ¹⁴C-radiolabelled herbicide to plantsto measure uptake and translocation of the herbicide. In addition to theadvantages of the apparatus in enhancing accuracy and uniformity ofspray application, the enclosure formed by the wind shield ensurescontainment of the radiolabelled material and permits effectivedecontamination.

[0086] The preceding description of specific embodiments of the presentinvention is not intended to be a complete list of every possibleembodiment of the invention. Persons skilled in this field willrecognize that modifications can be made to the specific embodimentsdescribed here that would be within the scope of the present invention.

What is claimed is:
 1. A process for spraying a plot with a liquid spraycomposition, comprising the steps of: (1) positioning in a field amobile shielded plot sprayer having a permanent reservoir, such that theenclosed area defined by the wind shield of said sprayer covers theplot; (2) adding a suitable quantity of a spray composition to thereservoir; and thereafter (3) initiating operation of the spray assemblyof said sprayer to move in a predetermined pattern across the plot andto spray the spray composition uniformly over the entire plot; whereinsteps (1) and (2) of said process are carried out in either order.
 2. Aprocess as set forth in claim 1 for consecutively spraying a pluralityof plots with liquid spray compositions, further comprising the stepsof: (4) releasing unused spray composition from the reservoir andrinsing the reservoir; and (5) repeating steps (1) to (4) on second andsubsequent plots until all plots have been sprayed.
 3. A process forspraying a plot with a liquid spray composition, comprising the stepsof: (1) positioning in a field a mobile shielded plot sprayer having aspray assembly adapted to receive a replaceable reservoir, such that theenclosed area defined by the wind shield of said sprayer covers theplot; (2) coupling a replaceable reservoir containing a spraycomposition to the spray assembly of said sprayer; and thereafter (3)initiating operation of said spray assembly to move in a predeterminedpattern across the plot and to spray the spray composition uniformlyover the entire plot; wherein steps (1) and (2) of said process arecarried out in either order.
 4. A process as set forth in claim 3further comprising the step of: (4) uncoupling the replaceable reservoirfrom the spray assembly and removing the reservoir from said enclosedarea through an aperture in the wind shield.
 5. A method of applying aliquid spray composition to at least one plot using a mobile plotsprayer, the method comprising the steps of: moving a mobile wind shieldto a location over said one plot such that the plot is at leastpartially shielded from the wind; delivering liquid spray compositionfrom a reservoir having an outlet located within the wind shield to aspray assembly of the mobile plot sprayer located within the windshield; and moving the spray assembly in a pattern within the windshield over the plot while spraying liquid composition.
 6. A method asset forth in claim 5 further comprising the step of moving the reservoiroutlet with the spray assembly in said step of moving the spray assemblyin a pattern.
 7. A method as set forth in claim 6 wherein the step ofmoving the reservoir outlet comprises moving the reservoir with thespray assembly.
 8. A method as set forth in claim 5 wherein the mobileplot sprayer includes a frame supporting the wind shield, and whereinsaid step of delivering liquid spray composition comprises withdrawingliquid spray composition from the reservoir supported by a mobile plotsprayer frame.
 9. A method as set forth in claim 8 wherein said step ofdelivering liquid spray composition comprises withdrawing liquid spraycomposition from the reservoir mounted on the spray assembly formovement therewith.
 10. A method as set forth in claim 8 furthercomprising the steps of removing the reservoir from the mobile plotsprayer and replacing the reservoir with a new reservoir.
 11. A methodas set forth in claim 10 wherein said step of removing the reservoirincludes passing the reservoir and the new reservoir through an aperturein the windshield.
 12. A method as set forth in claim 5 wherein saidstep of moving the spray assembly comprises the step of initiatingoperation of a computer program directing movement of the spray assemblyover the plot.
 13. A method as set forth in claim 5 wherein said step ofmoving the spray assembly comprises moving a second track along a firsttrack supporting the second track within the wind shield and moving thespray assembly along the second track.
 14. A method as set forth inclaim 5 wherein said step of moving the spray assembly comprises movingthe spray assembly exclusively within a single plane.